1) If you don't care about driving enjoyment and prefer a soft/comfortable/quiet car with huge space combined with bulletproof reliability, economy and resale; the camry it is.
2) If a fun to drive car at the cost of slightly less refinement/comfort is ok, then the altima is your choice; it has the smallest backseat of the three cars you mention though.
3) If you want an average car that excels at nothing but is fairly good with everything then the accord is where it's at.
4) However, I recommend that you also consider the Mazda 6. It's not as popular as the others only due to bad marketing by the dealer. But test drive one and you might just forget about the other three. It's that good a car. Also the best looking and there's nothing the other three have which it doesn't.
I love cars/driving so you can take that as a fairly well informed assessment of the cars in question. In the end however, just remember that you cannot go wrong with any of those four. The best car is the one your heart wants so leave your mind at home. Best of luck:-)